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| Study and authors | Agent used | Patient sample | Results |
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| Spoov et al., 2010 [28] | Thyrotropin-releasing hormone (TRH), 12.5 mcg i.v. | 19 drug-naïve patients with schizophrenia | Prolactin response negatively correlated with poverty of speech and inattention |
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| Spoov et al., 1991 [27] | TRH, 12.5 mcg i.v. | 20 patients with nonaffective psychosis | Prolactin response to TRH positively correlated with “nonparanoid” symptoms, such as thought disorder |
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| Cabranes et al., 1982 [78] | TRH | Patients with acute and chronic schizophrenia treated with chlorpromazine for 14 days | Increased prolactin response to TRH following chlorpromazine treatment |
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| Brambilla et al., 1976 [79] | TRH, 500 mcg i.v. | 20 patients with chronic hebephrenic schizophrenia, off medication for at least 10 days; 8 healthy controls | Enhanced prolactin responses to TRH in patients, despite normal basal prolactin levels |
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| Naber et al., 1980 [80] | TRH, 0.2 mg and luteinizing-hormone releasing hormone (LHRH), 0.025 mg | 22 patients with chronic schizophrenia (10 male, 12 female) receiving antipsychotics for 6–21 years | Attenuated prolactin response to TRH with long-term treatment; no relation between TRH response and psychopathology |
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| Mokrani et al., 2000 [13] | Clonidine, 0.35–0.375 mg depending on body weight | 134 drug-free in-patients—31 schizophrenia, 16 schizoaffective, 87 major depression—and 22 controls | Blunted prolactin response to clonidine in patients with paranoid schizophrenia, compared to controls and patients with disorganized schizophrenia |
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| Sharma et al., 1999 [25] | Fenfluramine, 60 mg orally | 35 drug-free patients—28 schizophrenia, 7 schizoaffective | Significant positive correlation between prolactin response to fenfluramine and negative symptoms, as measured by the BPRS |
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| Monteleone et al., 1999 [30] | Fenfluramine, 30 mg orally | 16 drug-free patients with schizophrenia; 16 matched controls | Greater prolactin response to fenfluramine in patients with resistant schizophrenia as per Kane’s criteria |
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| Abel et al., 1996 [26] | d-Fenfluramine | 13 drug-naïve patients with schizophrenia; 13 matched controls | Greater prolactin response in patients; positive correlation of prolactin response with affective symptoms—anxiety, guilt, and depression—measured on the BPRS |
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| Lerer et al., 1988 [14] | Fenfluramine, 60 mg orally | 10 drug-free patients with “chronic schizophrenia”; 10 matched controls | Blunted prolactin response to fenfluramine in patients |
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| Krystal et al., 1993 [81] | m-Chlorophenylpiperazine (m-CPP), 0.1 mg/kg i.v. | 12 drug-free patients with schizophrenia; 15 controls | Lower baseline prolactin in patients; no difference in m-CPP response; m-CPP triggered positive symptoms in patients |
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| Iqbal et al., 1991 [15] | m-CPP, 0.25 mg/kg orally | 7 male patients with schizophrenia; 8 male controls | Blunted prolactin response to m-CPP in patients; m-CPP worsened positive symptoms in this group |
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| Markianos et al., 2002 [82] | Clomipramine 25 mg i.v. | 25 male patients with schizophrenia, pre- and posttreatment with clozapine or olanzapine | Significant increases in prolactin following clomipramine; this response was blocked by both drugs |
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| Cowen et al., 1985 [83] | L-tryptophan, 7.5 g i.v. | 18 patients with schizophrenia on treatment and healthy controls | Increased prolactin response to L-tryptophan in patients |
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| Nerozzi et al., 1990 [84] | Growth hormone-releasing hormone (GHRH), 1 mcg/kg | 18 drug-free male patients with schizophrenia; 18 matched controls | Transient increase in prolactin following GHRH; no difference between the two groups |
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| Cantalamessa et al., 1985 [85] | Gonadotrophin-releasing hormone (GnRH) | 11 male patients with “acute schizophrenia” | Increased prolactin in 2 of 11 patients following GnRH |
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| Keks et al., 1990, 1992 [16, 17] | Haloperidol, 0.5 mg i.v. | 44 drug-free male patients with “acute schizophrenia”; 28 healthy controls | Blunted prolactin response to haloperidol in patients; basal prolactin positively correlated with the BPRS depression score. Maximal blunting seen in patients diagnosed with schizophrenia as per Kraepelin’s criteria |
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| Copolov et al., 1990 [18] | Low-dose haloperidol, i.v. | 46 male in-patients with psychosis (27 schizophrenia, 7 affective, 12 other psychoses); 28 male controls | Lower prolactin response in patients with schizophrenia than in controls, even after correcting for age |
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| Kulkarni et al., 1990 [29] | Haloperidol, 0.5 mg i.v. | 24 drug-free male patients with psychosis | Significant inverse correlation between prolactin response and the severity of delusions |
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| Keks et al., 1987 [19] | Haloperidol, 0.5 mg i.v. | 14 drug-free male patients with schizophrenia; 14 matched controls | Blunted and slow prolactin response to haloperidol in patients |
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| Nerozzi et al., 1990 [20] | Domperidone, 20 mg | 16 drug-free male patients with schizophrenia or schizophreniform disorder; 16 male controls | Blunted prolactin response to domperidone in all patients, more prominently in the schizophreniform group. Basal prolactin was comparable to controls |
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| Nerozzi et al., 1992 [86] | Domperidone, 20 mg | 17 elderly, drug-free male patients with schizophrenia; 8 age-matched male controls | Increased prolactin response to domperidone in patients; comparable baseline prolactin |
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| Monteleone et al., 1985 [21]# | Sodium valproate, 800 mg | 18 women with “chronic schizophrenia”; 20 healthy women | Valproate suppressed prolactin in normal women, but failed to do so in those with schizophrenia |
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| Scheinin et al., 1985 [22]# | Apomorphine, 0.005 mg/kg s.c. and 0.015 mg/kg i.v. | 11 patients with schizophrenia on medication; 8 controls | Apomorphine significantly decreased prolactin in controls but not in patients |
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| Whalley et al., 1984 [87]# | Apomorphine, 0.75 mg | 19 drug-free patients with psychosis; 9 healthy controls | Increased suppression of prolactin by apomorphine in patients with schizophrenia compared to controls |
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| Ferrier et al., 1984 [31] | Apomorphine, 0.75 mg s.c. | Unmedicated patients with acute and chronic schizophrenia; healthy controls | No difference in the response to apomorphine across groups; however, basal prolactin was negatively correlated with the severity of positive symptoms |
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| Rotrosen et al., 1978 [23] | Apomorphine and L-dopa | Unmedicated patients with chronic schizophrenia; healthy controls | Slightly blunted suppression of prolactin in patients compared to controls with apomorphine; greater suppression in patients than controls with L-dopa |
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| Kolakowska et al., 1981 [88] | Apomorphine 0.05–0.1 mg/kg | 17 patients with schizophrenia on treatment | No relationship between antipsychotic dose and apomorphine-induced prolactin suppression |
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Tsuchiya 1984 [24] | Experimental stress | Patients with schizophrenia, hypomania, depression, and alcohol dependence; healthy controls | Stress-induced prolactin release significantly greater in patients with schizophrenia than in controls |
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